I was recently helping a customer on a forced convection electronics cooling analysis and they asked me how to account for a thermal impedance contact between a chip and the PCB. They have a value of 0.00075 C-m^2/W. Right now CHT v2 only supports a “thin layer resistance” model for contact resistances. With some manipulation, the effect of the thermal impedance can be accounted for within SimScale.

Below is how I manipulated thermal impedance to an equivalent thickness and thermal conductivity.

Inverting the original thermal impedance gives us units that most engineers are more comfortable with; the units are not quite thermal conductivity (W/m-K) as there is an extra “m” term in the denominator, but it is close.

Next, I can arbitrarily assume a contact thickness; in this case I choose 0.1 mm. By multiplying the contact conductance by the thickness, I end up with a thermal conductivity value of 0.1333 W/m-C.

Lastly, while choosing the Thin Layer Resistance model in CHT v2, I define the thermal conductivity as 0.1333 Q/m-K and a thickness of 0.0001 m.

Please let me know if you have any questions.